The purpose of this proposed research is to develop a sophisticated membrane system into a hemodialysis unit which will function in a mode similar to a biological kidney; for the first time an artificial kidney will produce a true urine-product. We shall construct a device which will imitate inorganic ion-selectivity and water retention. These goals will be accomplished by utilizing: 1) the process of chemical etching for forming staged, tortuous microcapillaries (10-250 mu diameter) which induce convective fluid flow. These capillaries have been proven to greatly reduce boundary layer effects, maximize the ratio of area of membrane to prime volume and reduce clotting because they can be easily heprinized; 2) a new method for producing ion-selective mosaic membranes is proposed; piezodialysis reversible yields piezoosmosis and dialysis reversible yields osmosis will be used to remove salts and water from the ultrafiltrate in order to concentrate the organic solutes; hence, a true urine-product will be formed. The salt and water will be returned to the patient after passing through an ion-exchanger to remove divalent ions; hence the dialysate wash will be totally obviated. The hemodialysis unit will become easily transportable. This unique system has the potential to become a truly implantable device. 3) experiments are proposed to determine the relationships between solute and solvent transport and hydrostatic and osmotic pressure for blood-membrane-solution systems and other biological fluids; these experiments will have important clinical value for understanding the disequilibrium syndrome associated with hemodialysis. Mosaic membranes will be used as a model for studying molecular transport in solute concentrations equivalent to biological solutions. These experiments will completely evaluate the mosaic membranes from the standpoint of irreversible thermodynamics. 4) the effect of surface charge upon thrombosis formation will be investigated by use of the unique circulating currents associated with ionic transport across ion-selective mosaic membranes.